Behind The Scene
A successful flight doesn't only involve the pilots and flight attendants.
From the Air Traffic Control, to the people who work at the gate, the maintenance and cargo guys, catering staff, and other personnel who are not visually present in the vicinity of the plane, are all responsible for a certain flight to happen.
These personnel whose responsibilities are not dealing directly with the passengers, are what I call the "behind the scene" personnel. They are there to make a contribution of their skills, to make the flight leaves on time with no issues, and bring passengers to their destination.
I acknowledge them and greet them with a smile. Let's give them too the credit that they deserve.